« ПретходнаНастави »
Combination Jar and Hand Squeezer The adaption of the jarring principle to the hand squeezer makes a combination machine of much practical value. This type (Fig. 5) is best adapted to deep work or on molds having deep green sand cores. The sand is jarred by means of a foot lever and the boards are then squeezed into place, the mold rolled over and the pattern drawn away from the mold. For use in steel foundries on small work this type of machine is one of the best.
The Importance of Proper Equipment It is of the utmost importance that the proper equipment be provided if the hand squeezer is to produce what it is capable
of producing. Do not expect any old flask or pattern arrangement to be good enough. It is quite possible to produce one or two molds with any sort of flask and pattern, provided time enough be given, but if you want production in quantities and the casting to be true to pattern, then you must provide the equipment which has been found necessary for rapid and accurate production.
When you hear of a foundry producing 250 molds a day on a hand squeezer, do not immediately conclude that such production is impossible. Look carefully into the equipment question and you may find the answer to the question, “Why can we only get 60 molds a day on our hand squeezers?”
Pattern Equipment Hand squeezers operate to an advantage over hand ramming even if the same pattern equipment is used. That is, on gated work which is rapped through the sprue hole. To get good results from gated work, a hard-sand match should be used, directions for making which are given elsewhere in this article. By this combination a considerable gain can be made over bench molding.
By attaching the patterns to a vibrator frame and having a good hard-sand match (Fig. 6), you save the time used in rapping the patterns by hand and obtain a casting closer to pattern, as the vibrator is attached to the frame and vibrates the patterns through the frame while the cope is being lifted and the patterns drawn. This is done without loss of time. Where the vibrator frame is used, care should be used in filling the flask with sand. If the sand is put in unequally so that it is more compact in one part than another, in squeezing you are apt to spring the pattern on the gate.
In the use of both of these pattern rigs you will notice only one half of the mold is squeezed at a time.
Patterns are sometimes mounted on boards (Fig. 7). Where the patterns are flat on one side, or where they are split in the center so one half can be mounted on each side of a board, this
method makes a very good and cheap pattern equipment and gives good results.
The board should be made from good dry stock. (Ash or oak makes a good board.)
The board may be built up with at least two layers and end pieces put on to prevent warping. After completing the board, it is a very good plan to let the boards soak in hot paraffine for a time. This will serve to preserve the boards in good shape.
In putting the patterns on the board there should be a good joint, so that no sand can get between the pattern and the board. A very small leather fillet (1-16") can be shellacked and pressed into the joint on some patterns and it makes a good job. This insures a mold without any ragged edges.
Aluminum and Steel Plates Aluminum plates where the patterns are cast on each side of the plate, (as described in this article) are much in use and give splendid satisfaction (Figs. 8 and 9). When the pattern is a new job, this can be made at no greater cost than the old way of making a gate of patterns.
If the job is a new one, the way to proceed is to make one master pattern, using aluminum shrink rule. From this make as many castings as you will want on the plate from a nonshrinking white metal. If carefully made, in fine sand, little finish is necessary to complete these white metal patterns.
By bedding these separate patterns in and carefully cutting the runner and gates, it can be easily cast together as described.
Probably there are more cast aluminum plates in use than any other kind, and too much cannot be said in their favor. Many firms contend that the saving in pattern repairs alone will pay the cost of the plate in a year.
Patterns that can be finished in a lathe and then pinned to each side of the plate (preferably a metal plate, either steel or sheet aluminum, Figs 10 and 11) make as good a pattern and plate as can be made.
Planished sheet steel plates are very satisfactory, and a great many are in use. Rolled sheet aluminum, about 3/8" thick, make excellent plates. They have the advantage of being very light and for that reason are preferred by many.
Where plates of this kind are used both cope and drag are squeezed in one operation. This materially reduces the time. The vibrator is usually attached to the plate and a good draw